1. Field of the Invention
The present invention relates to a clutch cover assembly, in particular for automotive vehicles, of the kind comprising a pressure plate, elastic means such as a diaphragm spring and a cover.
2. Description of the Prior Art
The invention is more particularly concerned with means for limiting the travel of the pressure plate to prevent the drive tangs, constituting the rotational linkage between and permitting axial movement between the pressure plate and the cover, tending to deteriorate when the pressure plate/diaphragm spring/cover combination is pre-assembled, but not yet bolted to the reaction plate. This situation occurs routinely, when pre-assembled units are kept in store, for example.
The function of the tangs in question is not only to link the pressure plate elastically to the cover, but also to contribute to urging the pressure plate to the released position on releasing the clutch, to prevent the pressure plate rubbing on the friction disk. For this purpose, these tangs are treated to provide sufficient elastic return force.
When the pre-assembled combination is not bolted to the reaction plate, the pressure plate is urged strongly outwards by the diaphragm spring. As the only force to resist this is that provided by the tangs, these are also urged outwardly until equilibrium is established between the return force of the tangs and the force of the diaphragm spring. The tangs are therefore deformed and this distension may result in deterioration of their return force properties.
Deterioration may also occur, even if expansion of the diaphragm spring is limited, during careless handling in particular, as when dropped, for example: by virtue of its non-negligible weight and inertia, the pressure plate may move away from the cover to an extent sufficient to bring about significant deterioration of the return force properties of the tangs.
For this reason it is important to provide means for limiting the travel of the pressure plate.
The provision of these means for limiting the travel of the pressure plate is not always indispensable, however.
Clutch cover assemblies supplied as original equipment are in most cases, after inspection, carefully stored in packing cases, with protective means placed between them, and delivered directly to the manufacturer for fitting on his production lines.
In view of the relatively limited number of handling operations, it is rare for clutch cover assemblies to be returned due to deterioration of the tangs.
This does not apply when the clutch cover assemblies are supplied as replacement parts, as they are then subject to numerous handling operations at all points in the distribution chain, and are sometimes stored in a careless manner, by being piled up, for example.
This leads to returns, the return force properties of the tangs having deteriorated as a result of impact, being dropped and other causes, especially in the case of clutch cover assemblies in which no means of limiting the expansion of the diaphragm spring are provided, there being equilibrium in the storage state between the return force exerted by the tangs and that exerted by the elastic means.
In French patent application No 82 01809, the assignees of the present inventor have previously proposed a method of limiting the travel of the pressure plate which may be utilized only on clutch cover assemblies intended for use as replacement parts.
These limiting means consist in a peg comprising a barrel and, as a general rule, two lugs incorporating a shoulder and elastically deformable towards one another. The peg is force-fitted or lightly crimped by means of its barrel in an appropriate bore formed either in the cover or in the pressure plate. The lugs which can deform elastically towards one another slide freely in a bore formed in a second of the two components, after the shoulders on said lugs which can deform elastically towards one another have passed through the bore.
The pressure plate is retained in the axial direction through the cooperation of the shoulders on these lugs with an abutment surface formed around the second bore.
Although generally satisfactory, the use of these pressure plate travel limiting means is not always easy in the case of certain clutch cover assemblies, and, broadly speaking, two types of problem have been encountered.
Firstly, in attempting to fit the pressure plate travel limiting pegs manually, it has been found that it is not always easy to force fit or lightly crimp the pegs into the bores provided to this end in the pressure plate or in the cover.
The diameter of the barrels of the pegs is not always constant and the manual insertion of the peg in the bore is sometimes rendered difficult by an excessive diameter.
Secondly, the use of the pegs in question is difficult where it is required to prevent slight radial displacements of the pressure plate. As is well known in this art, in certain cases an impact to the edge of the clutch cover assembly applies buckling loads to at least one tang, even with such pegs fitted. Further bending of only a few hundredths of a millimeter can generate stresses with deleterious consequences as to the return force properties of the tangs, through exceeding their elastic limit. As the radial gap between the bore and the lugs of the peg is of the order of a few tenths of a millimeter, it can be seen that the pressure plate may easily move a few hundredths of a millimeter as a result of inertia.
The present invention is directed towards a clutch cover assembly in which the insertion of the pegs is significantly facilitated. In one advantageous embodiment, the pegs may also serve to retain the pressure plate in the radial direction.